21220624 has 20 divisors (see below), whose sum is σ = 43534044. Its totient is φ = 9986048.

The previous prime is 21220613. The next prime is 21220627. The reversal of 21220624 is 42602212.

It can be written as a sum of positive squares in 2 ways, for example, as 5760000 + 15460624 = 2400^2 + 3932^2 .

It is not an unprimeable number, because it can be changed into a prime (21220627) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38737 + ... + 39280.

Almost surely, 2^21220624 is an apocalyptic number.

It is an amenable number.

21220624 is an abundant number, since it is smaller than the sum of its proper divisors (22313420).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21220624 is a wasteful number, since it uses less digits than its factorization.

21220624 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78042 (or 78036 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 21220624 is about 4606.5848521437. The cubic root of 21220624 is about 276.8552202527.

Adding to 21220624 its reverse (42602212), we get a palindrome (63822836).

The spelling of 21220624 in words is "twenty-one million, two hundred twenty thousand, six hundred twenty-four".